Data storage systems contain one or more non-volatile storage devices, such as magnetic disk drives, electronic flash drives, and/or optical drives, and are used by one or more host devices (“hosts”) to store data to and retrieve host data from the non-volatile storage devices they contain. Specifically, data storage systems process host read and write input/output (“I/O”) operations they receive from hosts. The host I/O operations indicate host data to be read from or written to the non-volatile storage devices contained in the data storage systems. Data storage systems include hardware and software that receives and processes incoming host I/O operations, and that organizes and secures the host data that is stored on behalf of the host devices on the non-volatile storage devices contained in the storage arrays.
Fault tolerance is an important consideration for data storage systems. Some previous systems have replicated host across multiple data storage systems, in order to provide fault tolerance.
The time that elapses between when a host issues an I/O operation to the data storage system and when the I/O operation completes is experienced as I/O latency by the host. I/O latency is an important performance consideration with regard to data storage systems.